I recently uploaded a new lecture to our online education courses; Equine Metabolic Syndrome.  I worry a little that the while the subject matter is one that most of my readers and students should know, the name may be confusing. Do you know what Equine Metabolic Syndrome means? Do you know about Insulin Resistance and what it means for your horses and their health?  It's when an overweight or obese horse develops a condition related to the obesity. They have abnormal fat deposition, exercise intolerance (lethargic and out of shape) and can develop serious medical conditions like laminitis. It's a little bit like Type II Diabetes in humans, but not close enough to use the same nomenclature (cause that would make it too easy for all of us).  While its something that has been going on in horses for as long as we’ve been putting them in stables and supplementing their feed but its something the scientific community has only been investigating for the last handful of years. And because the syndrome is old but the research is new, there is a lot of misinformation out there about why horses are fat and what we can do to fix it. One of the myths I have the hardest time debunking is that of Hypothyroidism. When people tell me their horse is hypothyroid I think of that line from A Princess Bride, “You keep using that word. I do not think it means what you think it means.” So let me tell you the schpeal that I give clients and other vets who call me for advice.

Hypothyroidism in a dog.
Back in the day, well not too long ago, people would notice that they had a horse that had become overweight and lethargic and they wanted to know why. In people and in dogs hypothyroidism is a real, documented disease and is somewhat common. Humans with thyroid dysfunction are fatigued, weak, irritable and gain weight, or have trouble losing weight. Dogs will become dull and listless, reluctant to engage in their normal activities and will gain weight despite no change in appetite or feedings. So it would only make sense that if your horse was now dull and pudgy that hypothyroidism would be the answer. So we started testing horses thyroid hormone levels and guess what? Sometimes they were low. ">Problem solved!!!  And thus hypothyroidism was blamed for a variety of equine problems such as obesity, laminitis, anhidrosis (inability to sweat), recurrent rhabdomyolysis (tying-up) and poor fertility.  But here’s the problem with that theory…. Thyroid hormone levels that we measure in the blood may not tell us about true thyroid function. And who cares what the numbers from the lab say if the thyroid gland itself is functioning properly and doing its job to aid in growth and regulation of metabolism? We also know that certain medications (Bute & dexamethasone), strenuous exercise and diets high in energy, protein, zinc and copper will falsely alter the levels of circulating hormones in the bloodstream. The only way to know about how the thyroid functions is to perform thyroid function tests, which are rarely done in the field because the medications needed to stimulate the thyroid (to prove to us that its working) are not readily available. But when horses that are showing the “classic” signs of hypothyroidism, and have low thyroid hormone levels are tested for true thyroid function, they are found to be normal. Researchers have even tried to prove this association by removing horse’s thyroid glands to see what happens. Well what doesn’t happen is they do not become obese and they do not develop laminitis.

“But I don’t understand!” you say. “I had a hypothyroid horse and we treated her and she got better! Was my vet wrong?” Well, yes and no. For all those years, we have been treating your horses correctly, using all of the knowledge that we knew at the time, but we were doing it for the wrong reasons. It has only been within the last few years that the veterinary community has come to define Equine Metabolic Syndrome. EMS is an endocrine disease of horses that is characterized by insulin resistance, meaning your horse’s cells don’t respond to insulin they way they should and the energy (glucose) they consume can’t be metabolized properly. It’s similar to Type II Diabetes in humans, in that it is often a result of obesity, rather than a cause. Some horses are more predisposed to being overweight, “easy keepers.” Obesity leads to insulin resistance, which in turn makes weight loss even harder to achieve. Horses with EMS are more prone to episodes of laminitis because of alterations in glucose and insulin in their blood streams. Many “hypothyroid” horses that have normal thyroid function will test positive for EMS and insulin resistance.

“So why does treating with thyroid medication make these horses better if they don’t have a thyroid problem?” you say. Excellent question! Well thyroid supplementation causes an increase in metabolism. By increasing the horse’s metabolism they are able to loose weight and correct their insulin resistance. It works so well that researchers are now recommending treating these types of horses with a much higher dose of thyroid supplementation, a “supraphysiologic dose.” So while we have been doing the right thing all along, we only now understand why it was working. It is important to understand one other big difference. True hypothyroidism, in dogs and people, will require life long treatment. Horses who have been successfully treated for EMS do not, and unnecessary treatment with thyroid supplementation over extended periods of time is not only a waste of money, but also a potential health risk.

   So if you have a horse that is slow, sluggish and fat, or one that has been previously diagnosed as hypothyroid, learn more about Equine Metabolic Syndrome by taking our online course and talk to your vet about what you can do to test and treat this very common condition.

Last post we talked about my horrible eating habits as a child and my misconceptions on how to formulate an equine nutrition protocol. Remember hay is not just a side salad, it is the basis of a diet, and grain is not a meal, just a multivitamin. So with that in mind let’s think about how we should adjust the horse’s diet to alter the number of calories being fed. First we have to do some math. Let’s say your dressage horse was burns ~23,000 calories per day. To get all of those calories into him, you gave 14,990 calories a day in hay and an additional 8,010 calories a day in the form of a complete performance feed. This is a diet that meets your calories requirements and is balanced and complete in vitamins and minerals.

Now imagine what will happen when your horse enters retirement and trades in his days of half-passes and piaffe for light hacks and trail rides. Because of his decreased activity he is now only burning 16,500 calories per day. If you continue to feed his old diet he will surely get fat! So what do you do? How do you decrease the amount of calories while maintaining a complete and balanced diet?

Most people will say, “Just cut back on his grain.” This is both good and bad advice. It is good that most people recognize that if we are going to alter anything we should alter the grain and leave the hay (the uber important fiber source) alone. The bad thing about just cutting back on the amount grain is you’re not just cutting calories.

This brings us back to the multivitamin analogy. Let’s say you take a multivitamin that for some reason contains 1000 calories but you are looking to loose a little weight by cutting back on your calorie intake (and exercising, right?). If you cut that multivitamin in half you will save yourself 3500 calories a week, that’s enough to lose a whole pound! Great right? Wrong, because by cutting that multivitamin in half, you may be halving your calories but you are also halving the amount of vitamins and minerals you are ingesting…not ideal.

That’s the same thing we do to our horses by just cutting back on the amount of the same old grain. You can’t keep giving him the same amount of grain because of the calories but you want to make sure you are providing the right levels of the essential vitamins and minerals. And if you feed a 1,000 pound horse half of the recommended amount of feed (the amount of complete performance feed intended for a 500 pound horse) you will be giving half the calories, sure, but also be giving half the nutrients. So what can we do? Well what would you do if it were you and the 1,000-calorie vitamin? You’d get a new vitamin! Right?!?

And that’s exactly what we should do for our horses, don’t just give a smaller amount of the same grain, get a different grain, one that has a more appropriate level of calories for your horse’s needs. There are so many good product lines on the market that contain multiple options for a complete balanced feed for horses at different activity levels. Pick one that’s right for your horse. Find a feed that will only provide 1,500 calories but still 100% of the recommended vitamins and minerals. Reed the feeding recommendations, they tell you what class of horse the feed is intended for: Maintenance (the lawn art), Light Work, Heavy Work, Pregnant/Lactating. Make sure you are always providing a complete balanced diet to your horse; regardless of how many calories he needs to keep his waistline in check and keep him eating out of your hands.
When I was little I used to help with the evening feedings at the barn after my lessons. In the same sequence every time, we dropped bales of hay down from the loft and I threw a few flakes into every stall while the barn manager mixed up everyone’s feed. As soon as that first bale hit the ground all hell broke loose! The barn shook with kicks to the wooden walls, buckets rattled on their hooks and teeth ran down the metal stall guards like a prisoner banging a tin cup across the bars. But as soon as I finished with the hay calm was restored and the barn sank into a satisfied silence of quiet chewing. The feed cart was then wheeled down the aisle and grain could be dumped into bins without fear of flying hooves or gnashing teeth.

I equated this pre-grain hay to the tiny salad brought out by the waiter at a nice restaurant. Placed on a tiny plate and consisting of a few pieces of lettuce, a ring of onion, one cherry tomato and a few croutons. It was meant to bridge the gap between the time when your mother cut you off from the bread basket (after your third or fourth breadstick) until your meal arrived. It wasn’t the meal itself and to me had no impact on my daily intake (I didn’t even factor it in when deciding what to order).

I know now that I was wrong. Salads can make fine meal, wonderful meals in fact, where all of your nutritional requirements are met and you are left sated. For humans we should strive to make the components of a salad the bulk of our diets, I bet we would be a lot healthier as a population. In horses it is even more important than that. Hay is not a side salad intended to keep horses calm while waiting for the real meal, in fact it should be the whole meal, the main component of a horse’s diet. It delivers calories, protein, and carbohydrates and as part of the carbohydrates, the most important element: fiber! Horses are hindgut fermenters; the microbes that live in their cecum and colon digest the fiber and produce molecules the horse can use for energy. Without fiber these good microbes would die, the horse would have no energy and worst of all the bad microbes (Salmonella and Clostridum to name a few) would take over and then we’re really in trouble.

So when I was a kid I was thinking about nutrition all wrong (for horses and probably for myself as well). We don’t build a diet around grain, adding hay just to keep the barn from being torn down at feeding time. We must build our horses entire nutritional program around hay. To do this we really should have our hay tested (every field and every cutting is a little different), to know exactly how many calories there are per pound and how much protein and carbohydrates our horses are getting. That way we can calculate exactly how much hay each horse needs (think 2-3% of their bodyweight per day, yes this means doing math and weighing your hay to know how much each flake weighs). The grain is the additive, only there to provide the vitamins and minerals that may be deficient in the hay (like Vitamin E and selenium) as well as some extra calories for the high performance horses who can’t eat enough hay to meet their caloric requirements. Rather than thinking of the hay as salad and the grain as the meal, we need to be thinking of the hay as the meal and the grain as a multivitamin, just filling in the gaps to make our total diet balance and complete.

When I was younger I really wanted a Swiss Army knife. I mean really, what kid wouldn’t? It's a knife AND scissors AND a nail file AND tweezers AND there is even a fake plastic toothpick! But as we were taught, with great tools comes great responsibility and Swiss Army knives weren’t just given out on a whim. I can’t remember which birthday it was (9th or 10th) when I finally got the small black Classic SD. But there was a trade off; if I was old enough to receive the coveted multi-tool device that also meant I was old enough to mow the lawn. So to me, mowing the lawn was part of an important rite of passage. I was now deemed responsible enough for not only a small sharp object, but a large, sharper motorized one!  And I enjoyed mowing the lawn, the challenge of getting it started (holding the pull cord with two hands and throwing myself back with all my might), the instant gratification, the smell of fresh cut grass. So when we moved to our current house, that sits on ¼ acre with a small fenced in backyard, I was happy to volunteer for lawn trimming services….until I met our mower.
“Its great,” he said. “It's a real mower.”  “As opposed to a ‘fake’ mower?” I responded. “No, a R-E-E-L mower,” he said with a smile. And then I saw it. It is a modern version of the old fashioned, non-motorized, blades spin in a circle in some scissor like motion, who even knows how the grass gets cut, probably what Tom Sawyer used after he was done white-washing Aunt Polly’s fence, mower. To get it to work, the blades have to be moving fast enough for it to cut the grass, rather than just bend it over, which (without a motor) takes a bit of work, and in such a tiny yard as ours, there’s not a lot of room to get a running start. And if the grass is too long it won’t work, you have to raise the blades, cut it once, lower the blades and cut it again! That is NOT what I consider instant gratification. But as much as I complain and refuse to ever help out in the yard (this also has to do with Chiggers, which we do not have where I grew up and who consider me a delicacy), the reel mower is cheaper (no gas/oil), quieter (he has no excuse not to listen to me while he mows) and is much better for the grass. So that now, just a week into spring, our lawn is thick and lush and needs to be mowed (by someone other than me) at least once a week.

Rotation of the coffin bone.
And while it is beautiful to look at, fresh, thick lush grass can also be dangerous. Pasture associated laminitis begins to occur after the growth of grass in the spring. In cases of laminitis, the lamina separates between the pedal bone (P3) and the inner hoof wall causing unrelenting pain and characteristic lameness. It is the most serious disease of the equine hoof that leads to devastating loss of function and sometimes loss of the horse. While there are many different conditions that can lead to laminitis, pasture associated laminitis, or “grass founder” can be traced back to the high sugar content of the grass.

When a horse takes in a large meal containing sugars, they develop a temporary inflammatory condition in the GI tract called “carbohydrate overload.” Starch and sugars are normally digested and absorbed in the stomach and small intestine. The transit time through this portion of the GI tract is about 90 minutes and with a balanced meal, most of the carbohydrates will be absorbed before the feed passes into the cecum and large colon. However, if the meal is too high is sugars, too many sugars enter the small intestine and instead of being properly absorbed, some pass through to the large colon. This leads to a shift in fermentation and acidity of the colon contents and allows dangerous toxins to leak out of the gut into the bloodstream. There is also a large spike in glucose and insulin in the blood stream.  These toxins, inflammatory substances, glucose and insulin reach the hoof and contribute to the formation of laminitis. Prevention of pasture associated laminitis can be as simple as limiting your horses’ access to lush grass.

However, some horses and ponies are more likely to develop laminitis (have a lower threshold) after consuming a high starch/sugar meal and require more than just limiting turnout time to prevent laminitis. All ponies and some breeds of horses (Warmbloods, Morgans and all “easy keepers”) are genetically predisposed to develop Equine Metabolic Syndrome (EMS). EMS is a disease characterized by obesity, abnormal fat deposition (crest neck, fat around tailhead and above eyes) and insulin resistance (IR). The cells in overweight horses stop responding to insulin and therefore cannot process sugars normally. Because of this, smaller amounts of grass may trigger a laminitic event in these animals. Diagnosis of EMS can be made by clinical signs, body weight and body measurements, and blood testing (insulin and glucose). Once an animal is diagnosed, the condition can be treated with diet, exercise and in some cases, medication.  Dietary recommendations include removing all concentrates (grain) from the diet (or feeding specially formulated low starch feeds), feeding grass hay only (no alfalfa) and limiting access to pasture. Any horse or pony who is obese, considered an “easy keeper,” or who has had a previous laminitic event should be tested for EMS. Equine Cushing’s disease can also lower the threshold for laminitis in horses on pasture. Older horses (>15 years) and horses with clinical signs of Cushing’s (curly haircoat, cresty neck, potbellied appearance, recurrent laminitis) should be tested and appropriately treated. These horses often have IR concurrently and testing for EMS is warranted in all cases of Cushing’s. Horses can be easily treated for Cushing’s disease with daily medication. Like EMS cases, Cushing’s horses should be managed even more carefully on pasture in the spring and summer.

The following suggestions are just a few things you can do to prevent pasture associated laminitis and keep your horses happy and sound throughout the spring and summer.

  1. Identify the horses and ponies who are at a higher risk of developing laminitis. Test “easy keepers,” geriatric horses and those with a history of laminitis for EMS and/or Cushing’s Disease.
  2. Treat any predisposing condition with diet, exercise and proper medications.
  3. For horses with a lower threshold, consider a zero grazing environment, such as a dry lot (while providing the horse with suitable forage alternatives).
  4. Limit turnout of pasture when grass is lush and when fructans are high.
  5. Turn horses out to pasture when fructan levels are likely to be at their lowest, such as from late night to early morning, removing them from the pasture by mid-morning.
  6. Employ the use of grazing muzzles to allow horses out on pasture but still limit their intake of grass.
  7. Maintain pastures regularly to prevent grass from becoming mature and stemmy (they contain high levels of fructans). 

If you have any questions about pasture associated laminitis and whether your horse is at a higher risk, contact your veterinarian for proper testing and specific recommendations that will work for you.